This invention relates to liquid developers for light-sensitive diazo-type copying materials, and, more particularly, it is concerned with improved liquid organic diamine developing solutions for 2-component diazo processes.
In the conventional dry ammonia gas process, a solution containing the diazo sensitizer, that is, the diazonium compound, one or more couplers, and an organic acid stabilizer, is coated upon a support sheet. The coated sheet then is exposed to light in contact with a translucent original. The latent image so obtained is developed by contacting the sheet with ammonia gas which neutralizes the acid stabilizer and promotes diazo-type coupling between the diazo and coupling materials to produce a dye image of the original. This ammonia process suffers from the disadvantage that ammonia fumes require ducting on the machinery used and extra ventilation in the rooms where the process is carried out.
To overcome this disadvantage of ammonia systems, a semi-wet process has been developed in the art. In this process, exposure is carried out as before. The latent image then is developed by applying an alkaline developing solution to the surface of the sheet. However, dry, high quality prints are difficult to obtain with liquid developers of the prior art. In general, the use of aqueous alkaline solutions produced lower image density than dry ammonia gas; often a less desirable hue is obtained; and development tends to be streaky or non-uniform. The copy sheets also are moist and require some form of drying.
Accordingly, it is an object of the present invention to provide a new and improved liquid developing solution for diazo-type processes.
Another object of the invention is to provide a liquid developing solution which is easy to apply, and which gives dry, high quality prints rapidly in diazo-type machines modified for liquid development using 2-component diazo papers.
A feature of this invention is the provision of an organic diamine developing solution which can be applied in small amounts rapidly and evenly in suitable roller application systems to provide dry, high quality prints quickly without heating and without objectionable pungent fumes from the process.